Carburetor



R. J. SMITH April 23, 1963 CARBURETOR 2 Sheets-Sheet 1 Filed Jan. 5, 1960 FIG.2.

INVENTOR. ROBERT J. SMITH mmuunm \HH HHHHHH AGENT pril 23, 1963 R. J. SMITH CARBURETOR Filed Jan. 5, 1960 F l G. 3

2 Sheets-Sheet 2 INVENTOR.

ROBERT J. SMITH AGENT 3,985,757 Patented Apr. 23, 1963 3,086,757 CARBURETGR Robert .1. Smith, St. Anns, Mm, assignor to ACE Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed .Ian. 5, 1960, Ser. No. 611 3 Claims. (Cl. 261-34) This invention relates to carburetors for internal combustion engines, and more particularly to a carburetor of the type having a horizontal mixture conduit above the fuel bowl thereof, referred to as a horizontal or side draft carburetor, such as used, for example, on outboard marine engines.

Among the several objects of the invention may be noted the provision in a carburetor of means providing for enrichment of the fuel-air mixture supplied to the engine by the carburetor under wide open throttle conditions utilizing the accelerating pump circuit of the carburetor; and the provision of such means, which may be referred to as a step-up system, in a horizontal carburetor such as above described wherein the accelerating pump is on the bottom of the fuel bowl of the carburetor. Other objects and features will be in part apparent and in part pointed out hereinaft'er.

The invention accordingly comprises the constructions hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a plan view of a carburetor in which this invention is incorporated, showing the carburetor mounted on an engine intake manifold;

FIG. 2 is a vertical section taken on line 2-2 of FIG. 1;

FIG. 3 is an enlarged vertical section taken on line 33 of FIG. 2; and

FIG. 4 is a fragment of FIG. 3 showing a moved position of parts.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the drawings, there is illustrated a horizontal or side draft carburetor C comprising a fuel bowl section 1, and a mixture conduit section 3 on top of the fuel bowl section having a horizontal mixture conduit 5. The fuel bowl section 1 comprises a cup-shaped body having a bottom 7 and an annular peripheral wall 9 providing a fuel bowl B. The mixture conduit section 3 is generally of T-shape, having a relatively large head '11 and a relatively small tubular stem 13. The mixture conduit extends horizontally through the head 11 from one end thereof to the other. It has an air inlet portion 15 in which is a choke valve 17 on a choke valve shaft 19. Inlet portion 15 leads into venturi portion 21 of the mixture conduit. Venturi portion 21 leads into throttle bore 23 in which is a throttle valve 25 on a throttle valve shaft 27. Shafts 19 and 27 extend horizontally transversely across the head 11. The latter is formed at its outlet end with a flange 29 for attaching the carburetor to engine intake manifold M (see FIG. 1).

The head 11 of the mixture conduit section 3 is formed with a skirt 31 having a groove 33 receiving the rim of the fuel bowl body 1. The stem 13 of section 3 extends down to the bottom 7 of the fuel bowl body. It is tubular, being internally threaded at its lower end as indicated at 35, and having a downwardly facing internal shoulder 37 adjacent its upper end. Body 1 and section 3 are held together by a screw 39 extending through a central hole 41 in the bottom 7 of body 1 and threaded in the lower end of the stem 13. Screw 39 constitutes a valve body, as will be later explained.

The head 11 of mixture conduit section 3 is provided with a horizontal tapped fuel inlet passage 43 for connection of a fuel supply line. A tapped hole 45 extends downward from passage 43 adjacent its inner end. Threaded in hole 45 and extending downward therefrom toward the fuel bowl B is a valve body 47 of the type shown in FIGURE 10 of US. Patent 2,969,785 and in which is slidable a valve 49. This valve 49 is controlled by an annular float 51 surrounding stem 13 in fuel bowl B. The float is carried by an arm 53 pivoted at 55 in the bowl, and has an arm 57 engaging a pin 59 which acts through a compression spring 61 on valve 49. As will be apparent, the arrangement is such that when fuel in bowl B is drawn down below a predetermined level, the float 51 swings down, allowing valve 49 to open for flow of fuel into the bowl. Then, when the predetermined level of fuel is attained, the float closes the valve.

A main fuel tube 63 has its lower end threaded in the stem 13 and extends up out of the stem into the venturi portion 21 of the mixture conduit 5. Tube 63 has a flange 65 engaging shoulder 37 and is provided with radial ports 67 within portion 21 immediately adjacent the bottom of the latter. Stem 13 has a metering orifice 69 between the upper end of screw 39 and the lower end of tube 63 through which fuel may flow from the bowl into the space in the stem above the upper end of the screw, and thence aspirated up tube 63 to the mixture conduit. This space constitutes a main fuel chamber and is specially designated 70. Flow of fuel through orifice 69 is under control of a metering screw 71 adjustably threaded in a member 73 extending outward from body 1. Thus, orifice 69, main fuel chamber 70 and tube 63 constitute the high speed circuit of the carburetor for supplying fuel to the mixture conduit 5 for admixture with air flowing through conduit 5 to the engine when the throttle valve 25 is open.

The carburetor C has an idle system comprising an idle tube 75 extending down across conduit 5 and into the bowl B from a horizontal passage 77 extending lengthwise of head 11 above conduit 5. Passage 77 is formed immediately inward from tube 75 with a restriction 79, and the flow from the upper end of tube 75 to this restriction is under control of an idle adjusting screw 81 adjustably threaded in the outer end of passage 77. Restriction 79 opens into a vertical recess 83 having a restricted opening 85 to the venturi portion '21 of the mixture conduit for admission of air to passage 77 downstream from the restriction 79. Downstream from recess 83 are recesses 87 and 89 intersecting passage 77 having idle ports 91 and 93 opening into the mixture conduit. A bowl vent is indicated at 94.

The fuel bowl section 1 is formed with an annular wall 95 extending down from its bottom 7. This wall is cylindric on the outside and conical on the inside, and defines an accelerating pump chamber 97 which is closed by a diaphragm 99. The margin of the diaphragm is clamped against the rim of wall 95 by a cup-shaped memher 101. This has an air vent 102. A stem 193 is vertically slidable in a central hole 165 in member 131 and has its upper end secured to the center of the diaphragm and its lower end projecting down below member 101. A coil compression spring 107 in pump chamber 97 biases the diaphragm downward to the retracted position in which it appears in FIG. 3. Fuel is adapted to enter pump chamber 97 from bowl B via an inlet passage 109, at the entrance to which there is provided an inlet check valve 111 adapted to open for flow of fuel from the bowl through passage 1119 to chamber 97 and to close under pressure of fuel in chamber 97 caused by upward flexing of the diaphragm.

Member 101 is formed with a downwardly extending lug 113. A pump lever 115 is pivoted at 117 on this lug for rocking movement'on a horizontal axis. The inner end of lever 115 engages the lower end of stem 103. -A link 119 connects a crank arm 121 secured on one end of throttle shaft 27 and the outer end of lever 115, the arrangement being such that when the throttle valve 25 is closed, the inner end of lever 115 is down (see FIG. 3), and as the throttle valve is opened, the inner end'of lever 115 is moved up to drive stem 103 upward and flex the pump diaphragm 99 upward against the bias of diaphragm return spring 107 through a discharge stroke. A spring 123, around shaft 27 and stressed between the carburetor head 11 and shaft 27, biases the throttle valve 25 toward closed position and the pump lever 115 toward its retracted position illustrated in FIG. 3, wherein the diaphragm is at the lower limit of its stroke, being held there by return spring 107. Manual operating means, such as a linkage 126, is used to open the throttle valve 25 against spring 123. Lever .115 has an extension 118, which makes operative contact with stem 103 as described. This lever extension 118 is constructed of flexible or resilient material so that at the limit of the upward motion of stem 103, extension 118 will flex to take up the over-travel of lever 115. Lever 115 may be an integral metal piece or can be constructed of two or more pieces providing the flexible portion 118.

The screw 39 has a head 125 at the top of pump chamber 97 formed with an annular groove 127 in which the upper end of diaphragm return spring 107 is seated. A sealing washer 128 is interposed between the head of the screw and the bottom 7 of body 1. Screw 39 has an axial recess 129 extending down from its upper end to a valve seat 131 for a ball check valve 133 contained in recess 129, and has an axial passage 135 extending down from the valve seat completely through the screw head 125. pump jet 137 is pressed in the upper end of recess 129. A coil compression spring 139 reacts from the upper end of the jet down against the ball 133 to bias the ball toward its seat 131. A pin 141 extends axially upward from stem 103 in line with passage 135 in screw 39. When the diaphragm 99 is in its downward retracted position, the upper end of this pin is below the seat 131 so that the ball may seat thereon. When the diaphragm is flexed upward past a predetermined point in its upward discharge stroke, the upper end of the pin engages the ball and moves it upward off its seat 131. The arrangement is such that engagement of the upper end of the pin with the ball occurs just before the throttle valve 25 reaches full open position, so that the ball is positively held off its seat 131 when the throttle valve is fully open.

Operation is as follows:

Whenever the throttle valve 25 is moved in opening direction (which is counterclockwise as viewed in FIG. 2), pump lever 115 is swung clockwise as viewed in FIG. 3. The inner end of the pump lever drives the stem 103 upward to flex the diaphragm 99 upward thereby to contract the pump chamber. This forces fuel from the pump chamber upward through discharge passage 135, ball K133 moving upward ofl its seat 131 against the bias of ball return spring 139, and the fuel is delivered into main fuel chamber 70 and thence up through the main fuel tube 63 to the mixture conduit 5. The fuel delivered by the pump is added to the fuel flowing from the bowl B through orifice 69 to chamber 70 and up through tube 63. The inlet check valve 111 closes when the diaphragm moves upward to prevent flow of fuel from pump chamber 97 back into the bowl B. When the throttle valve moves in closing direction, the diaphragm return spring 107 drives the diaphragm back downward, thereby expanding the pump chamber 97, and priming it with fuel from bowl B via passage 109, valve 111 opening and valve 133 closing for this purpose.

Assuming that the throttle valve 25 is fully opened, and held fully open, pin 141 engages ball 133 and positively holds it in open position off its seat 131. Then, normal flow of fuel through orifice 69 and up the tube63'is augmented by a flow of fuel through passage 1439, pump chamber 97 (valve 111 being open), passage and pump jet 137 to main chamber 70 and thence up the tube 63. Thus, under these circumstances, passage 109, pump chamber 97, passage 135 and pump jet 1337 provide a fuel by-pass from bowl B around orifice 69 to main chamber 70 to supply additional fuel under wide open throttle conditions for enrichment of the mixture of fuel and air supplied to the engine.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in. a limiting sense.

I claim:

1. A carburetor comprising a fuel bowl, a mixture conduit, a throttle valve in said mixture conduit, a stem extending from said mixture conduit into said fuel bowl and having a main fuel chamber, a passage in said stem connecting said fuel bowl and said main fuel chamber to said mixture conduit, an accelerating pump comprising a pump chamber, a pump member movable to expand and contract the pump chamber, means forming an inlet passage for supplying fuel from said bowl to said pump chamber and a discharge passage from said pump chamber to said main fuel chamber, a discharge check valve within said discharge passage, a linkage interconnecting said throttle valve and said movable pump member for operating said movable pump member to pump fuel in response to opening movement of said throttle valve, said linkage including a resilient lever to provide overtravel of said lever in throttle opening direction.

'2. A carburetor comprising a fuel bowl, a mixture conduit, a throttle valve in said mixture conduit, a stem extending from said mixture conduit into said fuel bowl and having a main fuel chamber, a passage in said stem connecting said fuel bowl and said main fuel chamber to said imixture conduit, an accelerating pump comprising a pump chamber, a pump member movable to expand and contract the pump chamber, means forming an inlet passage for supplying fuel from said bowl to said pump chamber and a discharge passage from said pump chamber to said main chamber, a discharge check valve within said discharge passage, a linkage interconnecting said throttle valve and said movable pump member for operating said movable pump member to pump fuel in response to opening movement of said throttle valve, and a pin mounted on said movable pump member for operating said discharge check valve at full open position of said throttle, said linkage including a resilient lever to provide overtravel of said lever in throttle opening direction.

3. A carburetor comprising a body structure forming a fuel bowl, a mixture conduit, a stem extending from said mixture conduit into said fuel bowl and a main fuel chamber, means forming a passage connecting said fuel bowl and said main fuel chamber to said mixture conduit, a throttle valve positioned in said mixture conduit, an accelerating pump having a pump chamber and a pump member movable to expand and contract the pump chamber, means forming an inlet passage for supplying fuel from said bowl to said pump chamber and a discharge passage from said pump chamber to said main chamber, a discharge check valve within said discharge passage, a linkage interconnecting said throttle valve and said movable pump member for operating said movable pump member to pump fuel in response to opening movement of said throttle valve, means for operating said throttle valve and said movable pump member simultaneously,

said linkage including a resilient lever to provide overtravel of said lever with respect to said movable pump member.

References Cited in the file of this patent UNITED STATES PATENTS 6 Fill Jan. 13, 1942 :Boller Nov. 10, 1953 Moseley et a1 June 28, 1955 Evinrude May 8, 1956 Kinney et a1 Mar. 17, 1959 Jones May 30, 1961 

1. A CARBURETOR COMPRISING A FUEL BOWL, A MIXTURE CONDUIT, A THROTTLE VALVE IN SAID MIXTURE CONDUIT, A STEM EXTENDING FROM SAID MIXTURE CONDUIT INTO SAID FUEL BOWL AND HAVING A MAIN FUEL CHAMBER, A PASSAGE IN SAID STEM CONNECTING SAID FUEL BOWL AND SAID MAIN FUEL CHAMBER TO SAID MIXTURE CONDUIT, AN ACCELERATING PUMP COMPRISING A PUMP CHAMBER, A PUMP MEMBER MOVABLE TO EXPAND AND CONTRACT THE PUMP CHAMBER, MEANS FORMING AN INLET PASSAGE FOR SUPPLYING FUEL FROM SAID BOWL TO SAID PUMP CHAMBER AND A DISCHARGE PASSAGE FROM SAID PUMP CHAMBER TO SAID MAIN FUEL CHAMBER, A DISCHARGE CHECK VALVE WITHIN SAID DISCHARGE PASSAGE, A LINKAGE INTERCONNECTING SAID THROTTLE VALVE AND SAID MOVABLE PUMP MEMBER FOR OPERATING SAID MOVABLE PUMP MEMBER TO PUMP FUEL IN RESPONSE TO OPENING MOVEMENT OF SAID THROTTLE VALVE, SAID LINKAGE INCLUDING A RESILIENT LEVER TO PROVIDE OVERTRAVEL OF SAID LEVER IN THROTTLE OPENING DIRECTION. 